Opposed table



June 20, 1961 E. c. KRUEGER OPPOSED TABLE Filed July 21, 1958 III III

INVENTOR. EDWAPD C. KEUEGEE BY z/mzm, d MJW/ United States Patent Office2,988,862 Patented June 20, 1961 2,988,862 OPPOSED TABLE Edward C.Krueger, Otsego, Micl1., assignor to Hammond Machinery Builders, Inc.,Kalamazoo, Mich., a corporation of Michigan Filed July 21, 1958, Ser.No. 749,934 2 Claims. (Cl. 51-240) This invention relates to a workfeeding means and particularly to a type thereof adapted for applying apressure of low but accurately controllable magnitude to a workpiece assame is fed to a work accomplishing device, such as a grinding wheel andparticularly to an electrolytic type of grinding wheel.

While the substance of the present invention is applicable in a varietyof work feeding devices, it has been developed for particularapplication to the feeding of the tool bits and similar small workpiecesto a grinding wheel. Therefore, the description will proceed withreference to this use, but such reference will be understood as solelyfor convenience in description and will not be limiting.

Frequently, the feeding of tool bits and similar small workpieces to agrinding wheel is handled manually, but in feeding large numbers ofsmall workpieces on a production basis to grinding wheels, it often isdesirable to provide suitable power feed apparatus utilizing a pressurefluid. In view of the greater initial cost, maintenance problems andother difficulties often incident to the use of hydraulic feedingdevices and since compressed air is normally available in most placeswhere grinding devices are used, it is especially desirable that suchfeeding apparatus be air driven. This, however, introduces otherproblems which are discussed below.

With more and further reference to an electrolytic grindingoperation,attention is called to the following circumstances and considerationswhich exist in the pracplied, the plunger of the power cylinder willoften stop in the mid-stroke in a well-known but nevertheless entirelyunpredictable manner. This is particularly true where a restrictedexhaust is used to slow the final approach to the end of the stroke.

(2) Some additional force must be applied to the table in order toovercome the inertia which develops when the table accelerates.

(3) Therefore, it is necessary with an elastic fluid [to supply sameunder a rather substantial pressure to the power cylinder in order tosecure its reliable operation and to positively prevent such stopping orhanging-up.

(4) Normally, in operating an electrolytic grinding machine, theoperator watches an ammeter which indicates the amount of currentflowing through the working surface of the workpiece, which currentunder a given set of conditions is a direct function of the pressureexisting between the workpiece and the abrasive surface. This pressureis held by the operator at the proper values indicated by the ammeterand is of sufliciently critical nature that it must be closelycontrolled for proper results.

(5) The workpiece is, in a typical usage, urged against the grindingwheel under a pressure of approximately 100 pounds per square inch ofworking surface of the workpiece. However, having in mind that suchworking surface is sometimes of the order of only one or twoonehundredths of a square inch in area, it will be recognized that insuch cases only one or two pounds of force need be applied to theworkpiece to urge it against the grinding wheel with the proper amountof pressure.

Thus, if the pressure is supplied to the power cylinder at such a valuethat it will apply only one or two pounds of pressure onto theworkpiece, it folows that only one or two pounds of force is desiredfrom the cylinder over that required to move the cylinder againstfriction and other resistances within the apparatus such as tableinertia. Thus, to keep the output of the cylinder at this low level, thepressure applied to the cylinder will be insuflicient to move theplunger freely and reliably and it will be too likely to hang-upunpredictably from time to time during otherwise normal operation of theapparatus.

Accordingly, a major object of the invention is to provide reliablyoperable apparatus utilizing an elastic pressure fluid for applying anaccurate, rapidly selectable, and closely controllable force ofrelatively low magnitude onto a work feeding device, such as the workcarrying table of an electrolytic type of grinder.

A further object of the invention is to provide apparatus in whichsufficient pressure can be applied to the power cylinder that it willoperate freely and reliably through repeated cycles of operations andwith no danger of hanging-up in mid-stroke, but which can neverthelessapply to a workpiece a total force of only one or two pounds urging itagainst a metal cutting device, such as a grinding wheel.

A further object of the invention is to provide a device, as aforesaid,wherein the adjustment of said output force through a wide range ofmagnitudes can be easily and rapidly effected by use of simplemechanism.

A further object of the invention is to provide a device, as aforesaid,wherein the output force thereof is subject to accurate control throughsuch wide range of magnitudes and, further, wherein when said outputforce is once selected it can either be maintained precisely withinnarrow limits of variation or accurately and rapidly further changed asdesired.

A further object of the invention is to provide a device, as aforesaid,which is sufiiciently simple in construction as to be capable ofmanufacture, installation, use and maintenance at very low cost.

A further object of the invention is to provide an apparatus, asaforesaid, which can be applied to convenient work feeding devices ofpresently known types without materialmodification thereof.

Other objects and purposes of the invention will be apparent to personsacquainted with devices of the general type upon reading the followingdisclosure and upon inspection of the accompanying drawings, in which:

FIGURE 1 is a front view of a grinding machine embodying the invention.

FIGURE 2 is a sectional view taken on the line 11-11 of FIGURE 1.

General description iln general, the objects and purposes of theinvention are carried out by providing a generally conventional pressurecylinder in operative association with a work feeding device, such as atable carrying device, in association with a metal cutting means, suchas a grinding wheel. A supply of pressure fluid of a substantiallyconstant pressure value is connected to said cylinder. Opposing thepressure cylinder is a suitable force producing device whose forceoutput is independent of the frictional effects within the pressurecylinder but which may be accurately and rapidly varied. A coil springis a typical device meeting these requirements and is arranged so thatthe force imposed by the spring will oppose movement of said workholding device in response to pressure supplied thereto from saidpressure cylinder. Thus, the net output force applied to feed the workis the difference between the pressure exerted by said pressure cylinderand the opposing pressure exerted by said coil spring. By suitablyadju'sting said coil spring, the opposing force exerted thereby isaccurately variable at will and within extremely close operating limits.

Detailed description Referring now to the drawings, there is shown oneform of apparatus by which the present invention may be carried out.This particular apparatus is, however, utilized merely for illustrativepurposes and it will be recognized that the disclosure herein set forthis not intended to be limiting.

Referring to the drawings, there is shown a grinding wheel 1 associatedwith a table 2 and a hood structure 3, all of which are set forth inmore detail in the application of March 29, 1956, Serial No. 574,728 andassigned to the same assignee as the present application. Said table issupported on the frame 4 of the machine for reciprocation therewith byany suitable means, such as the ball bearing structure generallyindicated at 6.

Referring now to FIGURE 2, there is shown a base plate 7 to which thetable 2 is mounted and which sup ports and moves the table toward andaway from the grinding wheel 1 in a manner set forth in detail in theabove-identified application, Serial No. 574,728. A fluid pressurecylinder 8 is mounted between the base plate 7 and the frame 4 in anyconvenient manner. In the particular embodiment herein shown, the casingof said cylinder is mounted through universal joint linkages 9 and 11,to the post 12, which is in turn mounted onto the frame structure 4. Theplunger 13 associated with said cylinder is mounted through anadjustable rod 14 and a yoke 16 to the base plate 7. Suitable pressurefluid means, not shown, are provided for supplying pressure fluid at aconstant pressure value to said cylinder 8 in the usual manner.

A plate 17 is affixed by a screw 18 to the forward side of the baseplate 7 and extends downwardly therefrom. Said plate 17 contains bearingmeans 19 therein rotatably supporting the shaft 21 which carries a handwheel 22 at its outer end and is suitably threaded at 23 inwardly fromthe plate 17. The leftward (as appearing in FIGURE 2) end 25 of theshaft 21 is of reduced size and slidably extends through a suitablebearing opening 24 in the structure of the frame 4. A reinforcing plate26 may be applied to said frame structure at the point through which theshaft 21 extends, if desired. A nut 27 is threaded on the threadedportion 23 of shaft 21 and a spring 28 is disposed between said nut 27and the plate 26.

A slide rod 29 is provided for prevention of rotation of the nut 27.Said rod is firmly received into a suitable opening 31 at the lower endof the plate 17, as by press fitting which may, if desired, bereinforced with a set screw or other suitable holding means, and saidrod extends through a further opening 32 in the frame 4 of the machine.The plate 26 may extend downwardly sufflciently to be in register withthe opening 32, and if so it is provided with a further opening'inregister with the opening 32 through which said slide rod 29 extends. Aspring backing plate or collar 33 is provided at the end of said sliderod 29 and a spring 34 is located between said spring backing plate 33and the adjacent structure of the frame 4.

Thus, the spring 28 will resiliently oppose movement of the base plate 7leftwardly with respect to the frame 4, which direction corresponds tomovement of the table 2 toward the grinding wheel 1, and the magnitudeof said resistance is determined by the adjustment of the nut 27 axiallyalong the shaft 21 in response to rotation of the hand wheel 22. Thespring 34 on the slide rod 29 resiliently cushions the rightward motionof the base plate 7 with respect to the frame 4, which corresponds tomotion of the table 2 away from the wheel 1.

Thus, when work is to be moved toward the wheel 1 on and by the table 2,and it is desired to have only a light pressure thereon between the workand the grinding wheel, the hand wheel 22 is adjusted so that theresilient force of the spring 28, when said spring is compressed to apoint corresponding to the point at which work is in contact with thewheel 1, is sufficiently less than the force exerted by the cylinderstructure 8, that the net force exerted by said cylinder structure ontothe feeding table for urging said work against the wheel 1 will be ofthe magnitude desired. In this way, the pressure supplied to thecylinder may be of sufficiently high magnitude that there is nopossibility of the cylinders hanging-up at some unpredictable point andtime in its operating cycle and yet the actual force applied to theworkpiece will be of whatever relatively low magnitude is desired.Further, the feeding pressure applied to the work can be readilyadjusted merely by adjusting the hand wheel 22 rather than engaging inthe more complicated and often time-consuming adjustments of thepressure of the cylinder actuating fluid as is required by some presentapparatus.

The spring 34 cushions the shock when the table is returned outwardly(rightwardly as appearing in FIGURE 2) which is also done under theforce and by the agency of the pressure of cylinder 8.

Although particular preferred embodiments of the invention have beendisclosed in detail above for illustrative purposes, it will beunderstood that variations or modifications of such disclosure, whichlie within the scope of the appended claims are fully contemplated.

What is claimed is:

1. A work-feeding device particularly adapted for feeding smallworpieces to a cutting tool, comprising: a frame; a work-supportingtable mounted on said frame for reciprocating movement; a cylinderhaving a piston slidable therewithin in response to the supply of fluidpressure thereto and means connecting one of said piston and saidcylinder to said frame and means connecting the other thereof to saidtable; a rotatable first shaft axially non-movably secured at one end tosaid table and means supporting the other end of said shaft for slidingmovement with respect to said frame, said shaft having a threadedportion; a nut threaded onto said threaded portion of said shaft; afurther shaft secured at one end to said table, the other end of saidfurther shaft being mounted for sliding movement with respect to saidframe, said further shaft being engaged with said nut to preventrotation thereof around the first mentioned shaft; a coil spring mountedon said further shaft and disposed between said other end thereof andsaid frame for cushioning return of said table away from said cuttingtool; a manually operable handle connected to said first shaft forrotating same and thereby causing said nut to move axially therealong;and a second coil spring surrounding said first shaft and disposedbetween said frame and said nut and operative to oppose movement of saidfirst shaft and thereby said table in one direction, the magnitude ofthe force exerted by said second spring being sufficiently less than theforce applied to said piston and cylinder that a net force of selectedmagnitude is applied to said table in a direction to urge said tabletoward said cutting tool, said second coil spring constituting the solemeans opposing movement of said table toward said cutting tool andthereby controlling the pressure with which the workpiece contacts thecutting tool.

2. A work-feeding device particularly adapted for feeding smallworkpieces to a cutting tool, comprising: a frame, a work-supportingtable mounted on said frame for reciprocating movement; a cylinderhaving a piston slidable therewithin in response to the supply of fluidpressure thereto; means connecting one of said piston and said cylinderto said frame and means connecting the other thereof to said table; arotatable shaft axially nonmovably secured at one end to said table andmeans supporting the other end of said shaft for sliding movement withrespect to said frame, said shaft having a threaded portion; a nutthreaded onto said threaded portion of said shaft; an elongated guideelement parallel with said shaft, said element being secured at one endto said table, the other end of said element being mounted for movementwith respect to said frame, said element being engaged with said nut toprevent rotation thereof around said shaft; a manually operable handleconnected to said shaft for rotating same and thereby causing said nutto move axially therealong; and a coil spring surrounding said shaft anddisposed between said frame and said nut and operative to opposemovement of said shaft and thereby said table in one direction, themagnitude of the force exerted by said spring being sufiiciently lessthan the force applied to said piston and cylinder that a net force ofselected magnitude is applied to said table in a direction to urge saidtable toward said cutting tool, said coil spring constituting the solemeans opposing movement of said table toward said cutting tool andthereby co ntrolling the pressure with which the workpiece contacts thecutting tool.

References Cited in the file of this patent UNITED STATES PATENTS1,212,257 Pokora Jan. 16, 1917 1,381,416 Heindl June 14, 1921 2,036,206Ernst Apr. 7, 1936 2,083,748 Steiner June 15, 1937 2,384,512 Wiken et a1Sept. 11, 1945 2,804,735 Comstock Sept. 3, 1957

